1. Field of the Invention
The present invention relates to an incubation and/or storage container assembly for gametes and/or at least one embryo and in particular for such a container assembly adapted for use in intravaginal incubation and culture for humans or other mammals.
2. Description of Prior Art
Conventional in-vitro fertilization (IVF) techniques are notoriously complex. They involve aerobic and sterile culture of embryos in Petri dishes at 37° C. in a 5% CO2 enriched atmosphere which requires cumbersome and expensive equipment such as a CO2 incubator operating 24 hours a day during the two or three days required for the fertilization and culture. It also involves delicate manipulations requiring the skills and dexterity of a laboratory biologist.
Intravaginal culture (IVC) has been developed and comprises maturation of gametes, fertilization of oocytes and embryo development in a sealed container filled with a suitable culture medium which is then placed in the vaginal cavity which serves as an incubator. This technology is disclosed in Ranoux U.S. Pat. Nos. 4,902,286 and 5,135,865. It is designed and utilized by assisted procreation specialists in their offices or clinics.
To date, IVC procedures have been performed with a polypropylene Cryotube manufactured by Nunc of Kamptrup, Denmark, which is closed after loading the gametes and sealed in a polyethylene Cryoflex envelope also manufactured by Nunc. IVC procedures using such a container assembly have numerous drawbacks. Many of these drawbacks are overcome with the container assembly disclosed in Ranoux et al U.S. Pat. No. 6,050,935. That patent describes a IVC container assembly comprising a container body and resealable closure means for selectively opening and closing a container body orifice. The container body has a main chamber with a cylindrical sidewall and a microchamber in communication with each other which permits the movement of one or more embryo(s) into and out of the microchamber. The microchamber has sidewalls of optical quality permitting microscopic inspection of embryos. The microchamber also facilitates the retrieval of one or more embryo(s) by means of a catheter without endangering the embryo(s). The container body is equipped with various valve designs which are either bulky or complex construction and/or uneasy to operate. A two-piece capsule of soft flexible material envelopes the container for lodgment in the posterior fornix.
When such a IVC container is taken out of the posterior fornix of the vagina, the outer capsule is removed and the embryos in the microchamber may be inspected under a microscope. One or more embryos is then retrieved from the microchamber by a catheter for transfer to the uterus. This is done while the patient is being prepared for the transfer of the embryo(s). The entire procedure is also designed to be carried out in an obstetrician or other assisted procreation specialist's office with a minimum of equipment.
One of the advantages of the IVC procedure is that fertilization and culture are carried out intravaginally where the atmosphere is naturally CO2 enriched and the amount of oxygen is much lower than of the ambient environment. Both properties are acknowledged as being beneficial, see Alan O. Trounson et al., Handbook of In-vitro Fertilization, CRC Press, Inc., 1993, p. 97 and Misao Fukuda et al., “Unexpected Low Oxygen Tension of Intravaginal Culture”, Human Reproduction, vol. 11, no. 6, pp. 1996, 1293-9. Likewise, the temperature is that of the natural environment of the vagina. Once the IVC container is removed from the vagina, it no longer benefits from this ideal natural environment. It is also known that the intravaginally CO2 enriched environment ensures the pH in the container is relatively constant and about 7.3 and that a lower level of CO2 in the container will cause a drop in the pH of the biological medium in which the embryo(s) reside. A relatively small change in the pH (say 0.5) may have drastic consequences over a long period of culture on the embryo(s).
An object of the present invention is to overcome such drawbacks of known IVC containers.
According to one aspect of the invention, a buffer chamber for CO2 enriched atmosphere is provided and cooperable with the vessel containing the biological medium gametes and/or one or more embryo(s) and is in communication with a CO2 permeable wall of the vessel. With such an arrangement, the vessel will remain in a CO2 enriched environment even after it is removed from the CO2 incubation environment or and in particular a vagina. Thereafter, the CO2 enriched air in the buffer chamber will be able to enter the vessel and compensate for any fall in the CO2 level inside the vessel and thereby mediate the pH in the biological medium. Indeed, it has been found if such a buffer chamber is provided on the incubation or storage vessel, the pH level of the biological medium in the vessel will fall only slightly over the period of about one or two hours after the removal of the container assembly from the CO2 enriched environment. Such a small dip in the pH level does not have any significant effect on the embryo(s) in the biological medium.
According to an embodiment, the buffer chamber comprises a shell mounted on the vessel with a CO2 permeable seal disposed between the vessel and the shell to prevent the ingress of liquids or other viscous fluids, in particular vaginal secretions while allowing the inflow of the CO2 enriched air from the surroundings and in the case of intravaginal incubation, from the vagina. In practice, the CO2 inflow rate of the permeable seal will be greater than the inflow rate of CO2 through the permeable wall of the vessel and very much greater than the CO2 outflow rate through the shell wall.
According to another embodiment, the shell is mounted for movement on the vessel between open and closed positions. The shell will be in its open position when the container assembly is introduced into a CO2 enriched air environment, such as a vagina in the case of intravaginal use, and is closed as soon as the container assembly is removed from the CO2 enriched air environment. In such an embodiment, the CO2 enriched air outflow may be virtually nil during the period between the removal of the container assembly from the CO2 enriched environment and the retrieval of the embryos from the vessel for transfer to a recipient, thereby ensuring CO2 equilibration in the biological medium.
In the course of residence in the CO2 enriched intravaginal environment, the level of oxygen in the buffer chamber will reach the favorably depleted O2 level which prevails in the vagina. Thus, after the container assembly is removed, not only is the air inside the buffer chamber advantageously enriched in CO2 but also reduced in O2.
According to an embodiment of the invention, the vessel is provided with a closure device including overlying disc-shaped valve members, each with an orifice, mounted for relative angular movement between an open position for access to the interior of the vessel and a closed position for sealing off access to close the vessel.
According to an embodiment, the peripheral flange of the outer disc-shaped member has a peripheral sidewall radially beyond the peripheral flange of the inner disc-shaped member. One of the peripheral flanges has protrusions selectively cooperable with cutouts in the peripheral sidewall in the other peripheral flange when the valve is in its closed position. Preferably, the peripheral sidewall of the outer disc-shaped member has one or more hooking members for snap fitting axial retention of the outer disc-shaped member on the inner disc-shaped member and/or a peripheral flange of the vessel.
One or both of a pair of opposed sidewalls of the microchamber has an abutment for docking a catheter at the desired location. A portion of the associated recess may define a lens face for viewing one or more embryo(s) in the catheter during or after retrieval from the microchamber.
The inner wall surface of the main chamber of the vessel tapers towards the microchamber. Thus, when the container assembly is received in the posterior fornix, that is in a substantially horizontal position, except when the recipient lays on her side, the inner wall surface slopes to a small zone, where gametes will tend to congregate, thereby enhancing the probability of contact between sperm and oocytes.
These and another objects and advantages of the invention will be brought out in the description of embodiments given by way of example with reference to the accompanying drawings.